Liquid separator, cooling system, and gas-liquid separation method

ABSTRACT

A liquid separator including a cylindrical closed container in which a refrigerant is stored, a refrigerant inflow pipe that allows the refrigerant to flow into the closed container, and a refrigerant outflow pipe that allows the vapor-phase refrigerant in a space inside the closed container to flow out, in which the refrigerant inflow pipe and the refrigerant outflow pipe are each connected from the upper part of the closed container toward the inside thereof, and the closed container has a short cylindrical shape in which the height is smaller relative to the diameter.

TECHNICAL FIELD

The present invention relates to a liquid separator, a cooling systemand a gas-liquid separation method, which are mainly used in a coolingsystem and separate a liquid flowing from an evaporator to a compressor.

BACKGROUND ART

In a cooling system including an evaporator, a compressor, a condenserand an expansion valve, an accumulator serving as a liquid separator maybe installed in front of the suction port of the compressor.

For example, the cooling system shown in Patent Document 1 is providedwith an evaporator, a compressor, a condenser, and a decompressionexpansion valve along the refrigerant flow path. The evaporator absorbsambient heat by evaporating the liquid-phase refrigerant. The compressorcompresses the vapor-phase refrigerant delivered from the evaporator.The condenser releases the heat of the refrigerant whose high pressureis increased by the compressor to condense the vapor-phase refrigerant.The decompression expansion valve decompresses and expands theliquid-phase refrigerant that has been cooled by the condenser.

This cooling system shown in Patent Document 1 is provided with a liquidseparator on the upstream side of the compressor that separates therefrigerant after passing through the evaporator into gas and liquid.

This liquid separator has a vertically elongated separation container asa whole. A refrigerant inflow pipe and a vapor-phase refrigerant outflowpipe are installed on top of the separation container. In addition, aliquid-phase refrigerant outflow pipe is installed at the bottom of theseparation container.

In this liquid separator, the refrigerant that has flowed into theinside through the refrigerant inflow pipe is centrifugally separatedinto a liquid-phase refrigerant and vapor-phase refrigerant whilerotating in the circumferential direction along the inner wall of theliquid separator of the separation container.

Subsequently, the vapor-phase refrigerant in the separation container isguided to the decompression expansion valve via the upper vapor-phaserefrigerant outflow pipe, and the liquid-phase refrigerant in theseparation container is guided to the evaporator via the lowerliquid-phase refrigerant outflow pipe.

On the other hand, a similar liquid separator is also shown in PatentDocument 2.

Similar to Patent Document 1, the liquid separator disclosed in PatentDocument 2 has a closed container formed vertically as a whole. At thebottom of this closed container, a first pipe that allows gas-liquidtwo-phase fluid to flow into the inside of the closed container, asecond pipe that discharges the gas in the closed container to theoutside, and a third pipe that discharges the liquid in the closedcontainer to the outside are connected.

PRIOR ART DOCUMENTS Patent Documents

-   [Patent Document 1] Japanese Unexamined Patent Application    Publication No. 2015-172469-   [Patent Document 2] Japanese Unexamined Patent Application    Publication No. 2013-120028

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

In the cooling system shown in Patent Documents 1 and 2, the compressoris located above the accumulator, and the liquid-phase refrigerantreturns to the accumulator by gravity.

Therefore, the accumulator is long in the vertical direction, and whenthe compressor is placed on the accumulator, the upper part of theliquid separator becomes heavy and the center of gravity is high. As aresult, the liquid separator becomes unstable, and so new technology hasbeen anticipated in order to remedy this point.

This invention was made in view of the above circumstances. Accordingly,the present invention provides a liquid separator, a cooling system anda gas-liquid separation method that enable a compressor to be placed ona closed container.

Means for Solving the Problems

In order to solve the above problem, the present invention proposes thefollowing means.

A liquid separator according to a first aspect of the present inventionincludes a closed container having a cylindrical shape in which arefrigerant is stored; a refrigerant inflow pipe that allows therefrigerant to flow into the closed container; and a refrigerant outflowpipe that allows a vapor-phase refrigerant in a space inside the closedcontainer to flow out, with each of the refrigerant inflow pipe and therefrigerant outflow pipe being connected from the upper side of theclosed container to the inside thereof, and the closed container beingformed in a short cylindrical shape in which the height is smallerrelative to the diameter.

A cooling system according to a second aspect of the present inventionincludes an evaporator that absorbs ambient heat by evaporating aliquid-phase refrigerant, a compressor that compresses a vapor-phaserefrigerant, a condenser that releases the heat of the refrigerant thathas been pressurized by the compressor and condenses the vapor-phaserefrigerant, and a decompression expansion valve that depressurizes andexpands the liquid-phase refrigerant cooled by the condenser along arefrigerant path, in which a liquid separator for gas-liquid separationof the refrigerant after passing through the evaporator is provided onthe upstream side of the compressor, the liquid separator has a closedcontainer having a cylindrical shape in which a refrigerant is stored; arefrigerant inflow pipe that allows the refrigerant to flow into theclosed container; and a refrigerant outflow pipe that allows therefrigerant in a space inside the closed container to flow out, theclosed container being formed in a short cylindrical shape in which theheight is smaller relative to the diameter.

A gas-liquid separation method according to a third aspect of thepresent invention comprising connecting a closed container having acylindrical shape in which the refrigerant is stored, with a refrigerantinflow pipe that allows a refrigerant to flow into and a refrigerantoutflow pipe that allows the refrigerant in a space inside the closedcontainer to flow out, and forming the closed container in a shortcylindrical shape in which the height is smaller relative to thediameter.

Effects of the Invention

According to the present invention, a liquid separator can be stablyheld even if a heavy compressor is arranged on the liquid separator.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a configuration diagram showing a cooling system including aliquid separator according to an embodiment of the present invention.

FIG. 2 is a configuration diagram showing a cooling system including aliquid separator according to the first embodiment of the presentinvention.

FIG. 3 is a perspective view showing a liquid separator according to thefirst embodiment.

FIG. 4 is a vertical cross-sectional view showing the internalconfiguration of the liquid separator shown in FIG. 3.

FIG. 5A is a diagram for explaining the operation of the splashprevention plate provided in the liquid separator shown in FIG. 3.

FIG. 5B is a perspective view showing a splash prevention plate shown inFIG. 5A.

FIG. 6 is a perspective view showing a modification 1 of a splashprevention plate.

FIG. 7 is a perspective view showing a modification 2 of the splashprevention plate.

FIG. 8 is a cross-sectional view showing a liquid separator according tothe second embodiment.

FIG. 9 is a perspective view showing a liquid separator according to athird embodiment.

FIG. 10 is a configuration diagram showing a cooling system includingthe liquid separator according to the third embodiment.

EXAMPLE EMBODIMENTS

A liquid separator 10 according to the embodiment of the presentinvention will be described with reference to FIG. 1.

The liquid separator 10 is located on the upstream side of a compressor3 in a cooling system 1, and is provided for gas-liquid separation of arefrigerant after passing through an evaporator 2, for example.

This cooling system 1 is provided with the evaporator 2, the compressor3, a condenser 4, and a decompression expansion valve 5 along arefrigerant flow path 1A. The evaporator 2 absorbs ambient heat byevaporating the liquid-phase refrigerant. The compressor compresses thevapor-phase refrigerant. The condenser 4 releases the heat of therefrigerant that has become high pressure by the compressor 3 tocondense (or forcibly compress) the vapor-phase refrigerant. Thedecompression expansion valve 5 expands the liquid-phase refrigerantsupplied from the condenser 4.

The liquid separator 10 located on the upstream side of the compressor 3has a cylindrical closed container 11 in which the refrigerant C isstored. Inside the closed container 11 are provided a refrigerant inflowpipe 12 for flowing in a vapor phase medium or a gas-liquid two-phaserefrigerant and a refrigerant outflow pipe 13 that discharges thevapor-phase refrigerant in the closed container 11 to the outside.

The refrigerant inflow pipe 12 and the refrigerant outflow pipe 13 areeach installed from the upper surface 11A of the closed container 11toward the inside of the container 11B. The refrigerant inflow pipe 12and the refrigerant outflow pipe 13 are arranged at a mutual interval aslarge as possible in the radial direction (R direction) of the closedcontainer 11.

Further, the closed container 11 of the liquid separator 10 has a heighth that is relatively small with respect to a diameter along the Rdirection, and is configured to have a short cylindrical shape as awhole.

In such a liquid separator 10, since the closed container 11 is formedin a short cylindrical shape, even if a heavy compressor 3 is arrangedon the upper surface 11A of the closed container 11, it is possible tohold the liquid separator 10 in a stable state without the upper part ofthe liquid separator 10 becoming heavy, that is, becoming so-called topheavy.

In such a vapor compression type cooling system 1, the vapor-phaserefrigerant that has absorbed heat H1 from the heat source by theevaporator 2 and evaporated is gas-liquid separated by the liquidseparator 10, compressed by the compressor 3 and then sent to thecondenser 4. Subsequently, the liquid-phase refrigerant, which iscondensed by heat dissipation H2 to a cold source in the condenser 4, isdepressurized to a predetermined pressure by the decompression expansionvalve 5 and sent to the evaporator 2 again.

Here, the liquid-phase refrigerant may not be sufficiently evaporated inthe evaporator 2 due to a decrease in the load of the heat source, afailure of the decompression expansion valve 5, and the like and may besupplied to the compressor 3 as a gas-liquid mixed flow. The phenomenonin which a liquid is supplied to the compressor 3 in this way is calleda liquid bag. When a liquid is supplied to the compressor 3, theperformance of the compressor 3 may be deteriorated or a failure may becaused. In order to prevent this, in the liquid separator 10 accordingto the embodiment of the present invention, the liquid is separated fromthe gas-liquid mixed flow after passing through the evaporator 2, andonly the gas is supplied to the compressor 3.

As described above, in the liquid separator 10 according to theembodiment of the present invention, the closed container 11 is formedwith a short cylindrical shape whose height (h) is relatively small withrespect to the radial direction (R direction). Accordingly, the heightof the entire cooling system can be lowered, and so even if the heavycompressor 3 is arranged on the upper surface 11A of the closedcontainer 11, the device as a whole can be installed in a stable statewithout becoming top heavy.

Further, in the liquid separator 10, the closed container 11 is formedin a short cylinder shape. Accordingly, the refrigerant inflow pipe 12and the refrigerant outflow pipe 13 can be arranged on the upper surface11A of the closed container 11 at a sufficient interval in the radialdirection (R direction).

As a result, in the liquid separator 10, it is possible to prevent theeffect of turbulence of the liquid level of the refrigerant caused byinflow of the refrigerant from the refrigerant inflow pipe 12 to theclosed container 11 from extending to the refrigerant flowing out to therefrigerant outflow pipe 13. Therefore, it is possible to preventbeforehand the situation of the liquid-phase refrigerant in the closedcontainer 11 flowing out from the refrigerant outflow pipe 13 as aresult of being churned.

First Embodiment

The liquid separator 200 according to the first embodiment of thepresent invention will be described with reference to FIGS. 2 to 7.

This liquid separator 200 is installed in the cooling system F.

As shown in FIG. 2, the cooling system F is provided with an evaporator100, a liquid separator 200, a compressor 300, a condenser 400, and adecompression expansion valve 500 in a refrigerant flow path(specifically, a pipeline) composed of refrigerant flow paths 610, 620,630, 640, and 650. The evaporator 100 absorbs the ambient heat H1 byevaporating the liquid-phase refrigerant. The liquid separator 200separates the refrigerant into gas and liquid. The compressor 300compresses the vapor-phase refrigerant discharged from the liquidseparator 200. The condenser 400 releases the heat of the refrigerantpressurized by the compressor 300 to condense the vapor-phaserefrigerant. The decompression expansion valve 500 decompresses andexpands the liquid-phase refrigerant cooled by the condenser 400.

The refrigerant supplied from the decompression expansion valve 500 viathe refrigerant flow path 650 absorbs heat H1 from the heat source bythe evaporator 100 and evaporates. The evaporated vapor-phaserefrigerant passes through the refrigerant flow path 610, the liquidseparator 200, and the refrigerant flow path 620 in this order, and issent to the compressor 300.

The vapor-phase refrigerant compressed to high temperature and highpressure by the compressor 300 is sent to the condenser 400 via therefrigerant flow path 630, radiates H2 to a cold source, and condenses.

After that, the liquid-phase refrigerant condensed in the condenser 400moves to the decompression expansion valve 500 through the refrigerantflow path 640 and is reduced to a predetermined pressure. Subsequently,the liquid-phase refrigerant is sent to the evaporator 100 again throughthe refrigerant flow path 650.

Here, the liquid separator 200 is arranged on the upstream side of thecompressor 300 and has a role of preventing the liquid-phase refrigerantfrom being sucked into the compressor 300.

Since the compressor 300 is designed to compress the vapor-phaserefrigerant, it is known that if the liquid-phase refrigerant is mixedin, it will lead to a failure (called a liquid-back phenomenon).Normally, the refrigerant completely evaporates in the evaporator 100and becomes only a vapor-phase refrigerant. However, in the evaporator100, when a disturbance such as a decrease in heat load occurs, therefrigerant may not evaporate and a part of the liquid-phase refrigerantmay remain. In that case, this liquid-phase refrigerant is sent to therefrigerant flow path 610. Therefore, the liquid separator 200 separatesthe liquid-phase refrigerant contained in the refrigerant and suppliesonly the vapor-phase refrigerant to the downstream compressor 300.

Unless there are restrictions on installation, it is preferable toconstruct the refrigerant flow path 620 while avoiding a structurehaving a reverse gradient with respect to the direction of gravity or aU-shaped structure. This is because if such a reverse gradient structureor U-shaped structure exists in the refrigerant flow path 620, theliquid-phase refrigerant condensed in the refrigerant flow path 620 willaccumulate at that portion when the cooling system F is stopped. In thisway, since the liquid-phase refrigerant that accumulates in therefrigerant flow path 620 is sucked into the compressor 300 togetherwith the vapor-phase refrigerant when the cooling system F is startednext time, despite the fact that the liquid separator 200 is installed,there is a risk of causing the liquid-back phenomenon in the compressor300.

With reference to FIGS. 3 and 4, the liquid separator 200 located on theupstream side of the compressor 300 has a cylindrical housing 210 thatserves as a closed container in which the refrigerant is stored. Insidethe housing 210 are installed a refrigerant inflow pipe 220 for flowingin a vapor-phase refrigerant or a vapor-liquid two-phase refrigerant anda refrigerant outflow pipe 230 for flowing out the vapor-phaserefrigerant in the housing 210 to the outside.

The refrigerant inflow pipe 220 and the refrigerant outflow pipe 230 areinstalled from the upper surface 210A of the housing 210 toward theinside of the container 210B. The refrigerant inflow pipe 220 and therefrigerant outflow pipe 230 are arranged at an interval in the radialdirection (R direction) of the housing 210. The refrigerant inflow pipe220 is connected to the refrigerant flow path 610 in which thevapor-phase refrigerant or the gas-liquid two-phase refrigerant from theevaporator 100 is guided. The refrigerant outflow pipe 230 is connectedto a refrigerant flow path 620 that guides the vapor-phase refrigerantto the compressor 300.

The vapor-phase refrigerant or the gas-liquid two-phase refrigerantafter passing through the evaporator 100 flows into the housing 210through the refrigerant inflow pipe 220, and the liquid-phaserefrigerant in the gas-liquid mixed flow falls to the bottom of thehousing 210 by gravity and accumulates there. On the other hand, thevapor-phase refrigerant in the gas-liquid mixed flow is sent to thecompressor 300 through the refrigerant outflow pipe 230.

The housing 210 of the liquid separator 200 has a height h relativelysmall with respect to a diameter along the R direction, and isconfigured to have a short cylindrical shape as a whole.

As described above, in the liquid separator 200, since the housing 210is formed in the shape of a short cylinder whose height h is relativelysmall with respect to the diameter in the R direction, even if thecompressor 300 with weight is arranged on the upper surface 210A of thehousing 210, it is possible to hold the compressor 300 in a stablestate.

Referring to FIG. 2 again, in the vapor compression type cooling systemF as described above, the vapor-phase refrigerant which evaporated byabsorbing heat H1 from the heat source by the evaporator 2 is compressedby the compressor 300 to attain a high temperature and high pressure,and then sent to the condenser 400. Subsequently, the liquid-phaserefrigerant, which is condensed by heat dissipation H2 to a cold sourcein the condenser 400, is depressurized to a predetermined pressure bythe decompression expansion valve 500 and sent to the evaporator 100again.

As shown in FIGS. 4 and 5A and 5B, below an inlet (opening for theliquid to flow into the liquid separator 200) 220A of the refrigerantinflow pipe 220, a mesh-shaped splash prevention plate 240 is installedto prevent the vapor-phase refrigerant C1 that is supplied through therefrigerant inflow pipe 220 from blowing up the liquid-phase refrigerantC2 that has accumulated in the housing 210.

In the housing 210, when the flow velocity of the vapor-phaserefrigerant C1 supplied through the refrigerant inflow pipe 220 islarge, even if the liquid-phase refrigerant is not mixed in therefrigerant C1, the liquid-phase refrigerant C2 staying on the bottomsurface of the housing 210 may be blown up by the momentum of thevapor-phase refrigerant C1. In this case, there is a risk that theblown-up liquid-phase refrigerant C2 will flow out from an outlet(opening for the liquid to flow out from the housing 210) 230A of therefrigerant outflow pipe 230.

Therefore, as shown in FIGS. 5A and 5B, the mesh-shaped splashprevention plate 240 is installed below the refrigerant inflow pipe 220.The mesh-shaped splash prevention plate 240 mitigates the impact of thevapor-phase refrigerant C1 on the liquid surface of the liquid-phaserefrigerant C2, thereby preventing the liquid-phase refrigerant C2 frombeing blown up.

As described above, in the liquid separator 200 according to the firstembodiment, since the housing 210 is formed in a short cylindrical shapehaving a height h relatively small in the radial direction (Rdirection), even if the heavy compressor 300 is arranged on the uppersurface 210A of the housing 210, the liquid separator 200 can be held ina stable state without becoming top heavy.

In the liquid separator 200, since the housing 210 is formed in a shortcylinder shape, the refrigerant inflow pipe 220 and the refrigerantoutflow pipe 230 can be arranged in the upper surface 210A of thehousing 210 at a regular interval in the radial direction (R direction).

As a result, in the liquid separator 200, the effect of undulation(turbulence) of the liquid level of the liquid-phase refrigerant C2caused by the inflow of the refrigerant from the refrigerant inflow pipe220 into the housing 210 is prevented from extending to the refrigerantoutflow pipe 230. Therefore, it is possible to prevent the liquid-phaserefrigerant C2 in the housing 210 from being blown up and flowing outfrom the refrigerant outflow pipe 230.

Further, in the liquid separator 200, providing the mesh-shaped splashprevention plate 240 below the inlet 220A of the refrigerant inflow pipe220 alleviates the momentum of the vapor-phase refrigerant C1 collidingwith the liquid surface to prevent undulation of the liquid level of theliquid-phase refrigerant C2. This also makes it possible to prevent theliquid-phase refrigerant C2 in the housing 210 from flowing out from theoutlet 230A of the refrigerant outflow pipe 230.

Further, in the liquid separator 200, there is no complicated structurecausing a large pressure loss in the flow path of the vapor-phaserefrigerant from the refrigerant inflow pipe 220 to the refrigerantoutflow pipe 230. As a result, in the liquid separator 200, it ispossible to prevent the so-called liquid back phenomenon to thecompressor 300 (damage to the pipeline and equipment of the coolingsystem due to droplets of the refrigerant flowing through the flow pathwith kinetic energy) while suppressing the pressure loss during thegas-liquid separation of the refrigerant.

(Modification 1)

In the above embodiment, a mesh-shaped plate is used as the splashprevention plate 240, but the present invention is not limited thereto.That is, as the splash prevention plate 240, a plate having a largenumber of through holes 240 a as shown in FIG. 6, for example, a platehaving a plurality of holes such as punching metal may be used.

(Modification 2)

Further, as the splash prevention plate 240, a net-like body formed byentwining a plurality of fibers 240 b as shown in FIG. 7, for example, ametal scrubbing brush processed into a flat shape may be used.

Second Embodiment

A liquid separator 200′ according to the second embodiment of thepresent invention will be described with reference to FIG. 8.

The liquid separator 200′ according to the second embodiment differsfrom the liquid separator 200 according to the first embodiment on thepoint of a liquid intrusion prevention plate 250 being provided belowthe outlet of the refrigerant outflow pipe 230.

In the liquid separator 200′ shown in the second embodiment, when theflow velocity of the vapor-phase refrigerant C1 is large, there is arisk of the force blowing up the liquid-phase refrigerant C2 stored inthe housing 210 being strong enough such that splash prevention isinsufficient with the splash prevention plate 240 alone. Therefore, inthe liquid separator 200′, in addition to providing the splashprevention plate 240 below the inlet (outlet when heading toward theliquid separator 200′) 220A of the refrigerant inflow pipe 220, theliquid intrusion prevention plate 250 for preventing suctioning of theliquid-phase refrigerant C2 is provided below the outlet of therefrigerant outflow pipe (the port through which the liquid flows fromthe liquid separator 200′) 230A.

As a result, in the liquid separator 200′ shown in the secondembodiment, by adding the liquid intrusion prevention plate 240 belowthe refrigerant inflow pipe 220, it is possible to prevent droplets ofthe liquid-phase refrigerant C2 from being sucked into the refrigerantoutflow pipe 230, whereby the liquid separation function can beimproved.

As the liquid intrusion prevention plate 240, in addition to a normalplate, it is possible to use a mesh-shaped plate shown in FIG. 5B, aplate having a large number of through holes shown in FIG. 6, a net-likebody (or cotton-like body) formed by the entwining of fibers shown inFIG. 7, or the like.

Third Embodiment

The liquid separator 200″ according to the third embodiment of thepresent invention will be described with reference to FIGS. 9 and 10.

The liquid separator 200″ shown in the third embodiment differs from theliquid separators 200 and 200′ shown in the first and second embodimentson the point of being provided with a liquid level sensor 260, amaintenance valve 270, and a control unit 700.

In the normal operation of the cooling system, the gaseous refrigerantis completely sent from the outlet of the evaporator 100, and theliquid-phase refrigerant is transferred from the evaporator 100 to theliquid separator 200 only when the operation becomes unstable due to adisturbance. At this time, due to the unstable operation theliquid-phase refrigerant C2 in the housing 210 gradually evaporatesduring the subsequent normal operation to become the vapor-phaserefrigerant C1, whereby the accumulation thereof is eliminated.

However, if the unstable operation occurs continuously, it is expectedthat the amount of the liquid-phase refrigerant C2 staying in thehousing 210 of the liquid separator 200 will gradually increase.

Therefore, in the liquid separator 200″ shown in the third embodiment,as shown in FIG. 9, the liquid level sensor 260 for monitoring theamount of liquid of the liquid-phase refrigerant C2 remaining in thehousing 210 is attached to this housing 210.

If the liquid level of the liquid-phase refrigerant C2 that accumulatesin the housing 210 becomes higher than the position of the dropletprevention plate 240, the droplet prevention plate 240 will not functionand the liquid separation function may be significantly reduced.

In this case, since the liquid-phase refrigerant C2 may flow out fromthe refrigerant outflow pipe 230 and cause liquid back, it will benecessary to stop the compressor 300.

Therefore, in the liquid separator 200″ of the third embodiment, asshown in FIG. 10, a control unit 700 is provided that monitors the valueof the liquid level sensor 260 of the liquid separator 200 and stops theentire cooling system F′ including the compressor 300 when the liquidlevel of the liquid-phase refrigerant C2 exceeds a limit value.

Then, in the liquid separator 200″ of the third embodiment, after thecooling system F′ is stopped, the maintenance valve 270 at the lowerpart of the housing 210 is opened and the accumulated liquid-phaserefrigerant C2 is discharged, whereby a return to the normal state canbe achieved.

The maintenance valve 270 may be opened and closed manually by anoperator, or may be opened and closed by a drive means operated by aseparately provided control unit 700.

Although the embodiment of the present invention has been described indetail with reference to the drawings, the specific configuration is notlimited to this embodiment, and includes design changes and the likewithin a range that does not deviate from the gist of the presentinvention.

Priority is claimed on Japanese Patent Application No. 2019-55600, filedMar. 22, 2019, the content of which is incorporated herein by reference.

INDUSTRIAL APPLICABILITY

The present invention is mainly used in cooling systems and can beapplied to a liquid separator, a cooling system and a gas-liquidseparation method that separates liquid flowing from the evaporator intothe compressor. Even if a heavy compressor is arranged on top of theliquid separator, the liquid separator can be stably held.

DESCRIPTION OF REFERENCE SYMBOLS

-   -   1: Cooling system    -   1A: Refrigerant flow path    -   2: Evaporator    -   3: Compressor    -   4: Condenser    -   5: Decompression expansion valve    -   10: Liquid separator    -   11: Closed container    -   12: Refrigerant inflow pipe    -   13: Refrigerant outflow pipe    -   100: Evaporator    -   200: Liquid separator    -   200′: Liquid separator    -   200″: Liquid separator    -   210: Housing    -   240: Splash prevention plate    -   250: Liquid intrusion prevention plate    -   260: Liquid level sensor    -   270: Maintenance valve    -   300: Compressor    -   400: Condenser    -   500: Decompression expansion valve    -   610: Refrigerant flow path    -   620: Refrigerant flow path    -   630: Refrigerant flow path    -   640: Liquid pipe    -   650: Liquid pipe    -   700: Control unit    -   C: Refrigerant    -   C1: Vapor-phase refrigerant    -   C2: Liquid-phase refrigerant    -   F: Cooling cycle    -   F′: Cooling cycle    -   R: Radial direction

What is claimed is:
 1. A liquid separator comprising: a closed containerhaving a cylindrical shape in which a refrigerant is stored; arefrigerant inflow pipe that allows the refrigerant to flow into theclosed container; and a refrigerant outflow pipe that allows therefrigerant that has flowed into a space inside the closed container toflow out, wherein: the refrigerant inflow pipe and the refrigerantoutflow pipe are each arranged from the upper part of the closedcontainer toward the inside thereof; and the closed container is formedin a short cylindrical shape in which the height is smaller relative tothe diameter.
 2. The liquid separator according to claim 1, wherein asplash prevention plate for preventing the scattering of refrigerantdroplets is installed near the outlet of the refrigerant inflow pipelocated in the closed container.
 3. The liquid separator according toclaim 2, wherein the splash prevention plate is composed of amesh-shaped plate.
 4. The liquid separator according to claim 2, whereinthe splash prevention plate is composed of a plate having a large numberof through holes.
 5. The liquid separator according to claim 2, whereinthe splash prevention plate is composed of a net-like body formed byentwining a plurality of fibers.
 6. The liquid separator according toclaim 1, wherein a liquid intrusion prevention plate for preventingintrusion of the liquid-phase refrigerant in the closed container isfurther provided near the inlet of the refrigerant outflow pipe.
 7. Theliquid separator according to claim 1, wherein the closed container isprovided with a liquid level sensor that detects the liquid level of theliquid-phase refrigerant and a control unit that stops the entire devicewhen the detected value of the liquid level sensor exceeds apredetermined limit value.
 8. The liquid separator according to claim 1,wherein a discharge valve for discharging the liquid-phase refrigerantis provided at the lower part of the closed container.
 9. A coolingsystem comprising an evaporator that absorbs ambient heat by evaporatinga liquid-phase refrigerant, a compressor that compresses a vapor-phaserefrigerant, a condenser that releases the heat of the refrigerant thathas been pressurized by the compressor and condenses the vapor-phaserefrigerant, and a decompression expansion valve that depressurizes andexpands the liquid-phase refrigerant cooled by the condenser along arefrigerant path, wherein: a liquid separator for gas-liquid separationof the refrigerant after passing through the evaporator is provided onthe upstream side of the compressor; and the liquid separator includes aclosed container having a cylindrical shape in which a refrigerant isstored; a refrigerant inflow pipe that allows the refrigerant to flowinto the closed container; and a refrigerant outflow pipe that allowsthe refrigerant in a space inside the closed container to flow out, thecylindrical closed container being formed in a short cylindrical shapein which the height is smaller relative to the diameter.
 10. Agas-liquid separation method comprising: connecting a closed containerhaving a cylindrical shape in which the refrigerant is stored, with arefrigerant inflow pipe that allows a refrigerant to flow into and arefrigerant outflow pipe that allows the refrigerant in a space insidethe closed container to flow out, and forming the closed container in ashort cylindrical shape in which the height is smaller relative to thediameter.